Irrigated Corn Response to Soil-Test Indices and Fertilizer Nitrogen, Phosphorous, Potassium, and Magnesium
- T. A. Obreza and
- F. M. Rhoads
Improved soil-water management techniques have made irrigated corn (Zea mays L.) yields of more than 12.5 Mg ha−1 possible in the southeastern USA. Data relating fertilizer rates and soil test indices to grain yield under intensive water management are needed to maximize fertilizer use efficiency. The objective of this study was to generate fertility index-yield response data from which critical levels of Mehlich 1 soil test P, K, and Mg could be calculated. Irrigated corn was grown at Quincy, FL during 1980 and 1981. Nitrogen was applied at 168, 336, and 504 kg ha−1, P at 0, 29, 59, and 118 kg ha−1, K at 0, 209, and 418 kg ha−1, and Mg at 0, 67, and 134 kg ha−1 in a total of 11 treatments. Indices of available nutrients were measured via the Mehlich 1 soil test prior to each season. For both years, a minimum application of 168 kg ha−1 of N, 29 kg ha−1 of P, and 0 kg ha−1 of Mg was required for maximum grain yield, which averaged 11.2 Mg ha−1. For K, maximum yield occurred with minimum applications of 209 and 0 kg ha−1 in 1980 and 1981, respectively. Calculated critical Mehlich 1 soil test levels were 9, 45, and 33 mg kg−1 for P, K, and Mg, respectively. Comparison of our results with current soil test rating categories and corresponding recommended fertilizer rates indicated that maximum corn yield was obtained with a P fertilizer rate which was 50 kg ha−1 lower than the recommended rate.
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